Every once in a while, my iPhone says it has full strength LTE and yet, inexplicably, it is somehow incapable of streaming Spotify or downloading a simple email. It's extremely frustrating, particularly when Wi-Fi isn't available. Luckily, if you suffer from this issue, there is a way to check your phone's actual signal strength — and ways to improve it if you're consistently having signal woes. Checking your iPhone's true signal strength is an old trick: Dial *3001#12345#* and then press the call button. When you do this, you're taken into Field Test Mode and it shows your signal strength not as a set of bars or dots, but in terms of decibels (dB), the scientific, logarithmic unit used to describe antenna signal strength. It will show a number between -40 and -130. The closer you are to -40, the better your signal is. Right now, mine shows -97 — pretty solidly mediocre. In this case, it corresponds accurately with three dots of signal strength, as depicted in the upper left of my phone's screen. On Android, you can check this information much more easily: Just head to Settings, About Phone, and the signal strength should be available under the Network or Status fields. Knowing the exact signal strength of your phone is well and good, but that information isn't all that useful unless you can do something about it. Before you try any home or store-bought solutions to fix persistent issues, record the dB levels you get from different places in your house, at work, and along your commute so you have a baseline comparison. Now, if you want an all-around, all-the-time boost in signal strength, you can try a signal-boosting case like the $60 Reach79, which promises to improve signal strength up to 2x. Re/code found it helped improve reception about half the time. By comparing your results post- to pre-case, you can see if it actually makes a difference in your phone's reception — objectively. If you find signal strength is poor at home, but fine everywhere else, you can buy a signal booster. In fact, your carrier may even provide one to you at no cost if it's a consistent issue that's making you consider switching carriers (AT&T, Sprint, T-Mobile, and Verizon all offer router-like microcells you can plug in at home to boost reception). Old homes and buildings that use plaster and chicken wire in the walls are notoriously bad for both cell and Wi-Fi signals. A DIY solution that boosts not only reception, but also audio, is putting your phone in a glass cup. Not so useful if you're trying to make a phone call, but if you just need a few more dBs to download that awesome new app or to stream Hot Chip without buffering pauses, it's a quick and easy fix. Just make sure there's no water in the glass before you drop it in first, okay? You can also use an app like Signal Tracker (free on Android) or a site like Open Signal to check where signal is strongest and weakest in your area, so you can avoid the dead zones. And while it may feel like it could help, waving your phone over your head usually does not result in picking up a stronger cell signal. But now, you can test that for yourself!